[Openexr-devel] Problems with Data Window

[Julie Santerre]

Hi!

I'm experiencing problems with exr data windows. I would really appreciate to have your advice...

I'm using the IlmImf library to read and write exr files. I did a lot of testing with the images t01.exr -- t16.exr from your download section and everything is working as expected. I'm also handling every other exr files from that download section. I can modify the data window and the display window of those exr files and the results are as expected when, for instance, I look at the resulting image in Nuke by reading a file previously written by my software. I can crop an image and I still get the expected result. So, until that point, everything is working perfectly...

My problems arise when I try to manipulate cropped exr files that was generated by Nuke using their own crop transformation. If I understand correctly what Nuke is doing, it only crops the data window and it keeps the display window as it is. This behavior makes total sense to me. My big problem is when I'm trying to read those cropped exr files generated by Nuke and write those back to file using my software. It seems to me that data is not aligned correctly in the resulting file. To write back the images correctly to file, I need to add an offset (when inserting slices in FrameBuffer) that depends on the size of the display window. This is not making any sense to me. My understanding is that the display window is not playing a role when writing a file, just when displaying it. Am I right?

So, in brief, I implemented a library that works perfectly with every exr file generated by your organization and by my own software. I do have problems with cropped files produced by Nuke (and by other software as well). Is there something I'm missing here? Maybe I'm not extracting all the information I need from the headers? Is there a data alignment I need to consider? Have you ever heard about any issues with cropped exr files generated by Nuke?

I hope I gave you enough details about my problem.

Thank you so much for your time,

Julie